1. Field of the Invention
The present invention relates to an apparatus for producing laminates, and in particular to an apparatus for producing laminates having a blower for blowing a gas near an extruding die.
2. Description of the Related Art
For producing laminates such as substrates for photographic printing paper, an extrusion laminate method (also referred to as extrusion coating method) is widely employed in which a resin film of thermoplastic resin such as polyolefin extruded from an extruding die is applied to a running substrate or web and press-bonded thereto by nipping the film and the substrate together at a nip point located between a nip roller and a cooling roller, thereby laminating the substrate with the resin film.
In the production of laminates, a various kinds of gases are blown from a blower provided near the extruding die for various purposes. For example, Japanese Patent Application Publication No. 63-246227 discloses that a gas that easily permeates through the resin film is blown toward the nip point at which the substrate and the resin film are nipped together in order to alleviate a troublesome situation in which very small pores (hereinafter referred to as xe2x80x9ccratersxe2x80x9d) are formed on the surface of the resin film applied to the substrate. In addition, Japanese Patent No. 2749381 discloses that an inert gas is blown toward the surface of the resin film on the cooling roller side to prevent odors, and an acidic gas is blown toward the surface of the resin film on the substrate side to enhance adhesion between the substrate and the resin film.
However, there is a disadvantage that because high-temperature thermoplastic resin is extruded in molten conditions from the extruding die, a volatile component volatilized from the resin film of thermoplastic resin is stuck and accumulated on the blower, and a part of the components is dropped onto the cooling roller, the nip roller, the substrate, the product and the like to smear the roller, product and the like. In particular, if the volatile component is dropped onto the product, not only the appearance but also quality of the product will be damaged. In addition, the volatile component may stick directly to the cooling roller and/or the nip roller to smear the roller.
If the product, roller and the like are smeared with such components, the production line should be stopped on a temporary basis to conduct cleaning, leading to a significant drop in productivity.
The present invention has been made in view of the above described situation, and its object is to provide a method and apparatus for producing laminates in which the blower, roller, substrate, product and the like are never smeared with a volatile component even in the case where a gas is blown from the blower placed near the extruding die when laminates are produced, thus making it possible to improve the quality and productivity of laminates.
For achieving the above described object, the present inventions is directed to a method for producing a laminate, comprising the steps of: coating a surface of a running substrate with a film of thermoplastic resin extruded in a molten condition from an extruding die; and nipping the substrate and the film together between a nip roller and a cooling roller to produce a laminate while replacing, with a gas blown from a blower placed near the extruding die, air in an area where the nipping is conducted, wherein before the thermoplastic resin is extruded from the extruding die, a volatilization temperature of a volatile component of the thermoplastic resin is determined and the blower is heated at a temperature not below the determined volatilization temperature.
According to the present invention, the volatilization temperature of a volatile component of the thermoplastic resin to be extruded from the extruding die is determined in advance, and the blower is heated at a temperature equal to or higher than the determined volatilization temperature before the thermoplastic resin is extruded from the extruding die, thus making it possible to prevent the volatile component of the thermoplastic resin from sticking to the blower for blowing the gas, which may improve adhesion between the substrate and the resin film or may prevent craters from being formed in the resin film, when a laminate is produced. Thereby, when a laminate is produced, the blower, roller, substrate, product and the like are not smeared with the volatile component even in the case where the gas is blown from the blower placed near the extruding die.
For the method for determining the volatilization temperature of the volatile component of thermoplastic resin, a measuring device may be used to actually measure the volatilization temperature, or a handbook of chemistry or the like may be consulted to determine the volatilization temperature referring to the components contained in the thermoplastic resin.
Preferably, the gas blown from the blower is heated at a temperature not below a temperature (xc2x0 C.) determined by subtracting 150 (xc2x0 C.) from the temperature (xc2x0 C.) at which the blower is heated. Thereby, a drop in temperature of the blower by the blowing of the gas is prevented, and the volatile component is prevented from sticking to the blower more reliably.
For achieving the above described object, the present invention is also directed to a laminate producing apparatus, comprising: an extruding die which extrudes a thermoplastic resin in a molten condition and coats a surface of a running substrate with a film of the thermoplastic resin; a nip roller and a cooling roller which nip the substrate and the film together; a blower which blows a gas around the extruding die; and a blower heater which heats the blower at a temperature not below a volatilization temperature of a volatile component of the thermoplastic resin.
According to the present invention, the blower is heated at a temperature equal to or higher than the volatilization temperature of the volatile component volatilized from the thermoplastic resin extruded in molten conditions from the extruding die by the blower heater, so that the volatile component is immediately volatilized without sticking to the blower. Thereby, the volatile component is prevented from sticking to the blower.
Preferably, the laminate producing apparatus further comprises a gas heater which heats the gas to be blown through the blower at a temperature not below a temperature (xc2x0 C.) determined by subtracting 150 (xc2x0 C.) from the temperature (xc2x0 C.) at which the blower is heated. Thereby, a drop in temperature of the blower by the blowing of the gas is prevented, and the volatile component is prevented from sticking to the blower more reliably.
For achieving the above-described object, the present invention is also directed to a laminate producing apparatus, comprising: an extruding die which extrudes a thermoplastic resin in a molten condition and coats a surface of a running substrate with a film of the thermoplastic resin; a nip roller and a cooling roller which nip the substrate and the film together; a blower which blows a gas around the extruding die, wherein a nozzle provided in a blowing face of the blower is located at a distance of at least 15 mm from an edge of the blowing face.
When a gas is blown from the nozzle, a negative pressure is provided in the surroundings of the nozzle to suck therein the air around the blower more easily, and thus the blower, rollers located near the blower and the product tend to be smeared with the volatile component. According to the present invention, the apparatus is configured to prevent this situation. Specifically, the nozzle is located at a distance of 15 mm or greater from the edge of the blowing face, thus preventing more reliably the surroundings of the blower from being influenced by the negative resulting from the blowing of the gas from the nozzle.
Preferably, at least one of a surrounding member and a brim-shaped member is provided on a periphery of the blowing face and surrounds the nozzle, so that the surroundings of the blower are hardly influenced by the negative pressure resulting from the blowing of the gas.
Preferably, a flow rate of the gas blown from the blower is not more than 50 mm/second.